function abs(mixed_number) {
  //  discuss at: http://phpjs.org/functions/abs/
  // original by: Waldo Malqui Silva (http://waldo.malqui.info)
  // improved by: Karol Kowalski
  // improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // improved by: Jonas Raoni Soares Silva (http://www.jsfromhell.com)
  //   example 1: abs(4.2);
  //   returns 1: 4.2
  //   example 2: abs(-4.2);
  //   returns 2: 4.2
  //   example 3: abs(-5);
  //   returns 3: 5
  //   example 4: abs('_argos');
  //   returns 4: 0

  return Math.abs(mixed_number) || 0;
}